


Primal Instinct

by WandererofStars



Category: Gravity Falls
Genre: F/M, Furry, Interspecies Romance, Oral Sex, Sex, Vaginal Sex, Werewolf Stan Pines
Language: English
Status: Completed
Published: 2018-11-13
Updated: 2018-11-14
Packaged: 2019-08-23 08:32:33
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 4,477
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16615538
Author URL: https://archiveofourown.org/users/WandererofStars/pseuds/WandererofStars
Summary: One night, you hear noises in the basement and goes downstairs to find out that, every full moon, the man of your wild fantasies resurfaces in wolf form and is searching for his mate...A commission written especially to the brightest star in the sky. ❤





	1. 1

**1.**

You were feeling particularly restless that night.

Thoughts involving a certain silver-haired man wearing a suit and a permanent grin who lived in a reclusive shack in the woods crawled in your mind, preventing you from falling asleep. You groaned against your pillow, feeling the familiar urges that always accompanied your memories of him.

You had lived in Gravity Falls for the first half of your life. Once or twice your parents had taken you to the Mystery Shack to see the odd creatures on display. You must have been around eight or nine. You watched him with fascination as he told his tall tales to the crowd. Once he had spotted you among the other ill-tempered children and you opened the brightest smile as he watched you. He smiled back and gave you a candy in secret, free of charge, ruffling your hair affectionately.

Years later, as your sixteenth birthday approached, you would ask to work for him claiming you were saving money for college. For some reason, he believed you, letting you organise the shelves, sweep the floor and, after coming to trust you, man the store (and the cashier) when he was away. For two glorious years that seemed to last an eternity, you were able to enjoy his company, even if it were at a respectable distance. Still, the sight of him in that suit, the sound of his hoarse voice, his sense of humor and the special moments you shared talking in the kitchen during breaks were like sunlight to a plant that had grown in dark places all their life. The man was just delightful.

Years passed since then. You went to college, got a degree and wondered what to do with your life when a brief glimpse of his face pulled you back to the past. You were sitting in your living room switching channels on TV when you saw Stan on an interview where he and his twin brother were talking about their latest expedition to the Arctic. They were back from a three-month investigation about portals and the supposed existence of alien bases on remote locations on the planet.

Stan had more wrinkles than you remembered and his hair had a stronger shade of silver. However, one thing had changed: he smiled more and looked less worried, as if a weight had been lifted from his shoulders. You wondered what had happened to him in the years you were apart. You also wondered if he knew you hadn’t stopped thinking about him ever since the day you left.

He never knew, but he was one of your first platonic loves. One responsible for many sleepless nights like this one.

* * *

**2.**

You got up that morning feeling cranky. Ford had spent the entire night working on his latest project. You had been having such a nice dream when a loud bang from downstairs woke you up. You cursed under your breath, rubbed your eyes and glanced at the alarm clock: three in the morning. You had barely gotten any shut eye that night.

Ever since Stan and his brother were back from the Arctic, you had returned to Gravity Falls to visit your father’s friend, Fiddleford McGucket. He had known you ever since you were a kid. Your dad had been a member of the Society of the Blind Eye and helped Fiddleford keep the town citizens blissfully unaware of the occult aspect of that place. Now, living in a wealthy mansion and with both his memories and his family back, Fiddleford welcomed you with open arms, inviting you to stay in one of his rooms.

Of course, none of it was mere coincidence. You happened to learn from the news that the Pines brothers were going back to gravity Falls to stay “with their good friend and research colleague Fiddleford.” This was the perfect opportunity to see Stanley once again.

You got up from your king-sized bed and picked up your phone to use as a flashlight to navigate the corridors. You glanced through the window. It was pitch black out there. The moon was hiding behind a blanket of clouds. But from the way a couple of moonbeams stubbornly shone through, you bet it was a full moon.

The mansion was quiet. Your footsteps echoed against the wooden floor. As you walked down the corridor, you noticed the door to the twins’ bedroom was closed. Dipper and Mabel must be sound asleep. The same went for Fiddleford’s bedroom. Ford’s bedroom was still open, meaning the man was still working on his research. You would have to remind him to shower before going to bed. His clothes had recently started to smell badly and there was a distinct stench that seemed to follow him wherever he went. Reclusive scientists and poor hygiene just seemed destined to go together like bread and butter.

As soon as you arrived at Ford’s lab, you found him sleeping _again_ on the sofa, his trench coat serving as an improvised blanket. His notes were sprawled on his desk, some of them having fallen to the floor due to the breeze that came in through the open window. There was a telescope pointed at the sky today. Why was Ford studying the stars? Wasn’t he working on the discoveries he brought with him from the Arctic?

You shut the window and closed the curtains, making sure the place was dark enough for him to sleep properly. You then opened a chest where some pillows and sheets were kept and threw one of them over his sleeping form, folding his coat and placing it on his chair. You glanced at his notes and saw drawings of a hairy, savage man beast. There were also notes on constellations and moon phases. You wondered if he and Stanley had come across such a creature during their travels.

Speaking of Stan…

 _Funny; I haven’t seen him all day. Or yesterday, for that matter.,_ you thought, glancing at Ford’s sleeping form. No, you couldn’t wake him up. He usually worked eighteen hours straight. Best to let the poor man get some sleep.

You left the lab, deciding to ask Fiddleford about Stan’s whereabouts when you heard another loud bang coming from the other side of the mansion. And then another. And another.

Ford groaned in his sleep, but he was so tired the noises didn't manage to wake him up. You wondered if it was Fiddleford who was making them or if it were an invader. Or invaders. You suspected it could be the gnomes. They had a habit of stealing food from homes and cafeterias. Maybe you could say hi to Jeff and invite him to share some raspberry pie with you. That is, if they hadn’t stolen it first.

You were halfway to the kitchen when you heard another bang. You stopped dead on your tracks once you figured the noise came from the basement.

There was nothing down there. Only equipment from the twins expedition to the Arctic and some of Fiddleford’s old personal junk from when he lived in the junkyard.

Something deep within you told you there was something **_wrong_ ** here. **Just what exactly had Stan and Ford found out in the Arctic**?

The house was supposed to be dead silent. Everybody was asleep at that late hour. You went to Stan’s room again and he was nowhere to be seen. He hadn’t come home for the past two days now. _Where was he?_

Against your better judgement, you decided to head down to the basement. Maybe the answer lay downstairs.


	2. 2

**3.**

You turned on the light on the stairwell and descended the metallic steps. Your footsteps echoed loudly and would surely warn whatever _thing_ was down there of your arrival. The banging suddenly stopped. Your blood froze in your veins. You were right. Whatever was making that noise wasn’t a machine. It _had_ to be alive and it heard you coming.

You arrived at the basement and your eyes were met with plenty of boxes piled up against the walls. The place felt crowded and claustrophobic. You wondered what were inside them. Did Ford and his brother really need all that for their research?

As you went further in, you saw a big square object in the far end covered with a thick beige cloth. As you approached it, you could hear _breathing_ coming from within, accompanied by a low menacing growl.

There was a creature underneath that cloth. A large creature. Probably the size of a lion, you estimated. Your phone was shaking in your hand from all your trembling. You could tell the creature was caged, but still. Ford must have placed a piece of cloth over it for some reason. Perhaps it was as dangerous as the Gremloblin. If you removed that cloth, staring into its eyes could make you go mad.

You heard it sniff the air a few times. The growling had ceased. You were too terrified to know what hid under that cloth and just turned around. You had barely walked two steps when you heard a whimper.

You swallowed hard, glancing at the covered cage again. The creature was whimpering, as if in pain or sad. It tugged at your heartstrings and you felt a strange pang of remorse at the thought of leaving it alone. Why hadn’t Ford said anything about there being a creature in the basement? Didn't you deserve to know when your life was in danger? You wondered if he was at least feeding it properly. You didn't want to wake up one day to a house full of half-eaten limbs and corpses lying around.

You fought back against your fear and walked back to the cage. You shut your eyes and pulled the cloth in one swift motion, revealing the caged monster. A brief yell escaped your throat as you stared at it. The abundant silver hair, the strong, sturdy build, wolfish features that evoked long forgotten desires, yellow eyes that pierced you with their penetrating gaze...

It _should_ be a wolf, but it wasn’t. It stood on its hind legs as it stared back at you.

A wolf that stood like a human. It was full moon. Ford’s sketches. The telescope pointed at the skies. Your whole face was illuminated when you realised what it was. But of course! This was a werewolf. Ford had found a werewolf in his expeditions.

The basement was too dark to see it properly. You increased the phone’s light and turned the screen at the creature. It winced at its brightness, growling at it. You felt nervous trying to lower the light to a comfortable intensity and slipped on something oily on the floor, falling on a pile of boxes.

Your phone flew from your hand and you could no longer see anything in the darkness. To your luck, the content inside the boxes wasn’t heavy, sharp or deadly in any manner. However, one particularly heavy object had fallen on your right leg and prevented you from moving.

You could hear the werewolf thrashing against his cage, hitting the iron bars with all his might. The noise would surely wake Ford or Fiddleford up. You prayed they would come and rescue you before that creature could eat you alive.

* * *

**4.**

Fiddleford was the first to hear the ruckus downstairs and practically fell out of bed once he realised the werewolf was trying to break free. He grabbed his taser, put on some pants and rushed to Ford’s lab, shouting at him until he woke up.

‘Git up, Ford! He’s at it again! C’mon! We can’t let’im break free!’

‘Alright, alright! I’m up!’ Ford replied, yawning loudly.

He reluctantly got up from the sofa and, still groggy, followed his friend to the basement. Once both men had arrived, they panicked at the sight before their eyes.

The chains holding the cage shut were coming loose. Soon enough, the werewolf would break free. Ford approached him carefully and took aim. The beast growled at him, baring his sharp teeth.  The man pulled the trigger, but the taser missed him by inches.

‘A little help here, Fiddleford!’

‘[_______] is injured! I need to help her!’ he said, kneeling down next to you, trying to lift the heavy boxes. ‘Ford, help me! This is too heavy!’

Soon, both men were trying to help you. The werewolf took the opportunity to bang his head against the door a few more times. They panicked once they saw the door to its cage open.

Ford aimed at it with his taser, shooting once, but the beast dodged it with lightning reflexes. A large paw knocked him out of the way as he advanced on you.

‘B-back off!’ Fiddleford yelled, shooting as well and missing his target. He was knocked out of the way just as his friend.

You stared at the werewolf in panic, shivering and breaking in a cold sweat. Tears rolled down your eyes as you started whimpering as he got closer. You couldn’t move. You couldn’t defend yourself. Your life was over. All you wanted was to see Stan again.

‘I’m sorry, **Stanley**...’ you moaned between sobs, weeping.

The werewolf stopped dead on his tracks. He towered over you, watching you in silence. He then raised his paw, claws as sharp as knives shining against the light…

...and he brought it down at one of the boxes, knocking a piece of equipment away.

He then crouched near you and, with some effort, raised the rest of the equipment, freeing your legs from their weight.  

Once he was done, the werewolf kneeled beside you like an overgrown wolf, his beautiful wild eyes watching you in silence like before. You stared back at him, a mixture of fear and awe in your face. That creature should be devouring you right now. Instead it just...watched you calmly.

You couldn't believe your eyes. Despite the wild wolf features and yellowish eyes, the face beneath all that hair was unmistakable…

‘Stan? Is that really you?’

The werewolf barked once, hearing his own name. This was so odd! You could recognise Stan Pines, proprietor of the Mystery Shack, former Mr. Mystery. But he looked so different! The lustrous silvery mane reminded you of his grey hair. The eyes looked more like a wolf’s now, but their shape still evoked the shape of Stan’s eyes. The square jaw was visible beneath the hair that trailed all the way to his ample chest, where it ended in an abundant mess of bodily hair.

Werewolf Stan shyly approached you, lowering his head so as to smell you. Hand trembling, you raised it until you brought your palm near his snout, praying he wouldn’t open those wide jaws full of sharp teeth. The werewolf slowly approached his face to your open palm, nostrils flaring as he smelled it. He licked your hand a couple of times and let you touch him. You caressed the cold snout and then his muzzle tentatively. He tried to lick your hand a couple of times again, making you giggle. You then sat upright and gestured for him to come closer. He let you caress his head and behind the ears, as if he were a pet dog. You saw him shut his eyes in delight as he enjoyed your affectionate touch.

Just as you were getting friendlier with the werewolf, Ford yelled for you to stay away from him and tried shooting again. Stan startled you as he leaped out of danger and rushed past Ford, heading upstairs. Ford yelled for him to stop and rushed after him while Fiddleford checked if you had any bites.

‘I’m fine. He didn't try to bite me.’ you answered.

‘What? Are you sure, [_____]? Even one bite could be fatal.’

You nodded.

‘That’s...unusual, to say the least. C’mon. We need to get you to safety.’

‘D’you think Ford can catch him on his own?’ you asked, remembering how quick the werewolf was.

‘No. He doesn’t stand a chance against it. And I told him that, many times over.’ he added, sounding annoyed. ‘I hope he doesn’t try anything stupid until I get to him. Though he still doesn’t listen to me as often as he should.’ Fiddleford admitted, helping you get up.

 

 


	3. 3

Fiddleford had insisted you stay at his mansion and lock all doors while he went to search for Ford and the werewolf. However, you refused to listen to him. You told Fiddleford you recognised Stan Pines and demanded he explain what happened to him.

‘Ah, you see, it’s complicated.’ he said, scratching his chin. ‘Ford told me he and Stanley found a hermit living near one of the places where a portal was sighted by the Air Force about five years ago. All investigation had ceased once some pilots went missing, but Ford insisted they should go investigate.’

‘A portal? He’s still trying to study anomalies, even after what happened in Gravity Falls last year?’ you asked in disbelief, remembering when Dipper and Mabel told you the events of the Weirdmageddon.

Fiddleford said he had tried to dissuade Ford many times, but that was his particular obsession, what with having six fingers in each hand and having been bullied as a child by mean kids who considered him a freak. He went on.

‘Turns out the portal was just an optical illusion. The reason why those pilots had disappeared was because of the wind storms that happened during a certain time of the year. But the worst was yet to come. You see, the hermit lived alone for a reason. Turns out he had a rare disease or genetic condition which made him revert to a more primal state during the full moon.’

‘A werewolf.’ you said.

‘Kind of. Stan told me he insisted they leave the place.’

‘I bet Ford refused.’ you said, not surprised.

Fiddleford shared a look with you, as if you had read his thoughts.

‘Ford wanted to stay and study that specimen. Two days later, it attacked Stan and Ford while they were getting ready to sleep and ended up biting Stan. Next thing we know, Stan became a werewolf.’

It was certainly an unusual story. But Fiddleford had no reason to make all of this up.

‘Is there any way to cure him?’

‘This is why Ford came to me. I believe there might be not just one, but two ways, in fact! But one of them still requires testing.’

At least Stan could be saved, you thought.

‘Do Dipper and Mabel know about this?’

Fiddleford shook his head. ‘No. And we intend to keep it that way.’

‘But you can’t just let the kids be in his company! It’s not safe!’

Fiddleford asked that you be silent for a moment. He thought he heard something coming from far ahead.

Even under the full moon, both of you had a hard time locating the trail left by Ford and the werewolf. After half an hour wandering in the woods, you heard shouting followed by growling and the noise of trees being hit. You could also feel the earth shake beneath your feet with the force of the werewolf’s stomping and jumping.

You found Ford having trouble using his phase gun to stun the werewolf. His purpose was to bring him back to the mansion so they could fill him with tranquilizers. It was the only way to stop Stan from attacking anyone until he had transformed back into a man.

The werewolf kept knocking Ford down into the ground and trying to bite him. But the scientist wore a holographic shield which ensured Stan’s teeth and claws couldn't even scrape him. Fiddleford took aim and hit the werewolf with his tranquilizer dart. Or at least he thought he did. The beast had leaped out of range a fraction of a second earlier and reappeared beside him, growling furiously. Knowing how this would end, you stood between Fiddleford and Stan.

‘[_____], what are you doing? Get behind me!’ he yelled, trying to pull you back, but you yanked your arm free of his grasp.

‘[______], are you mad? He’ll bite you!’ Ford shouted, getting up and taking aim once again.

‘Shut up, Ford! He’s not going to attack me!’ you shouted back.

Both men went silent and shared a look, thinking you were out of your mind. You stared at the werewolf and he stared back at you. There was a silent communication going on between you. He wasn’t growling anymore. Fiddleford watched both of you, intrigued. His mind seemed to be working on a theory.

‘Ford, we should back away slowly.’

‘What?’ he thought his friend had lost his mind.

‘Trust me.’

Ford still had his doubts, but his friend managed to convince him to put some distance between you and them. They watched from afar your interaction with the beast.

As predicted, the werewolf relaxed seeing the danger had passed. He slowly walked toward you, wagging his tail. He smelled you again and kneeled, letting you pet his head. All of a sudden, he hugged you and you felt his snout rub against your neck, making you giggle. He licked your skin, tail wagging even more intensely.

He remembered you. Even in wolf form, Stan still remembered you.

The two scientists watched as the werewolf picked you up with both arms and carried you bride style to a secluded part of the forest. He climbed a hill until he went inside a cave and didn't emerge again.

Fiddleford patted Ford’s shoulder and said it was time to go.

‘What? Are you just going to leave her in there, all alone with my brother?’

‘That’s exactly what I’m doing.’ he answered with a big smile, dragging Ford back to the mansion.

**Notes for the Chapter:**

> Are you ready to be alone with the big, bad wolf?


	4. 4

You had surrendered to the feeling of Stan’s caresses as he licked your pussy.

His face was buried between your legs, with his snout occasionally rubbing against your clitoris as he licked your folds. You didn't know what excited you more: to feel the contact of his warm wet tongue against your sensitive skin or to watch him pleasure you.

‘Stan...’ your voice wavered as you called his name. He emitted a low growl in response.

His tongue was larger than the ordinary tongue of a man. And it didn't seem to stop anytime soon. You were red and swollen, and you could feel your pussy throbbing hard. Soon your moans became louder and you grabbed his head, pressing it against your folds. You were desperate for release.

‘ _Stan_...’ you called him again, begging with tears in your eyes.

He surprise you by ceasing the ministrations of his tongue and coming to rest on top of you, rubbing his cock against your folds. He barked once at you, rubbing again. Then he lay down on the haystack next to you, pulling you toward him as both of you were in a sitting position, his paws holding you steady against him. The gears in your mind turned and you understood what he meant.

‘You want me to grind against you?’

A bark told you you were right. He was also staring at you with his mouth hanging open as he panted, looking rather silly. You giggled at the adorable sight.

You positioned yourself and straddled him, feeling his cock between your legs. You started rubbing your clitoris and your folds against his member, vigorously. He was hard and hot against you and your need for release screamed inside you. You had to cum.

You were practically bouncing on top of him, going up and down as you grinded, hearing his low growls against your ear as you worked. With one paw, he held you steady, while with the other he squeezed and slapped your butt cheek. You frictioned your clitoris against him desperately. The heat between you was unbelievable. The contact of flesh against flesh was driving you nuts. Without warning, a powerful wave came over you and you rode it, like a surfer rides a wave at sea. You felt waves of orgasm come crashing down, over and over as you grinded, with Stan holding your hips steady and helping you maintain the intense rhythm. You just kept riding that wave until you were spent and your legs were tired.

Stan held you in front of him so you wouldn’t fall backwards. You were sweaty and tired, but satisfied. Deeply satisfied. You buried your head against his hairy neck and he licked your neck and shoulder, rubbing his snout affectionately against you. Once you had recovered, he moved to rest on top of you. He licked your face again and stared deep into your eyes, as if asking for your permission. You caressed his head and nodded, feeling safe in his company.

He gently bit your shoulder as he positioned himself in front of your entrance and went in slowly, letting you get used to his size. When he saw you weren’t in pain, he went further in, plunging all the way to the hilt. He then began pumping his cock inside you in rhythmic motions, slowly at first.

The full moon rose above the clouds, shining bright in the sky. You let the werewolf make love to you tonight, enraptured by his wild scent and beastial nature, surrendering your entire being to your primal instinct.

* * *

**The next day…**

Fiddleford climbed the hill, phaser gun in hand. Ford had stayed inside to watch over the twins.

Cautious, he entered the cave, checking if the coast was clear. The werewolf was nowhere to be seen. He dared take a few more steps and soon found Stan’s sleeping form next to yours, his arms around your waist. Both of you snuggled in your sleep, bare naked. There was also bonfire that had long gone out.  

The scientist took out an electronic equipment and pierced the tip of Stan’s index, taking a tiny sample of blood from him. He placed it inside the device and waited for it to finish its analysis. As he did so, he averted his eyes from your naked forms.

The results came in. The component was down to five percent. And the substance was up to eighty percent.  

He walked out of the cave, sending Ford a text message. As he opened his backpack and took out some clothes for Stanley to wear once he woke up, he let out a relieved breath that everything had worked out. He stared once again at the text he sent and wondered about how Stanley would react once he woke up next to you, bare naked in a remote cave. Knowing Stan, he would be lucky if he didn't have a stroke. What mattered was that the werewolf problem was contained and everything could be back to their normally abnormal state in Gravity Falls.

 


End file.
